The invention relates to the field of medical devices and methods used in the treatment of diseases such as cancer which have the ability to metastasize within a patient""s body. More specifically, the invention is directed to methods and devices for locating sentinel lymph nodes associated with a lesion site within a patient""s body so that the sentinel lymph nodes may thereafter be selectively removed and analyzed to determine whether disease has spread from the primary lesion site to the sentinel lymph nodes. In the case of breast cancer patients, such methods and devices may eliminate the need for complete axillary lymph node dissection in patients who do not require such invasive and debilitating procedures.
With regard to breast cancer patients specifically, the determination of the severity of the disease or staging is frequently determined by the level of lymph node involvement in those lymph nodes which correspond to the primary cancer lesion site in the breast. The lymph nodes which correspond to the breast area are typically located in the armpit or axilla of the patient and are connected to the breast tissue of the patient by a series of lymph ducts. Other likely areas for sentinel nodes include inframammary and submammary locations and elsewhere in the patient""s chest. The sentinel lymph nodes can be in fluid communication with other surrounding lymph nodes, however, lymph drainage from the lesion site will first flow to the sentinel lymph nodes. Thereafter, lymph fluid drainage may then continue on to lymph nodes surrounding the sentinel nodes.
Studies have shown that by the time a typical breast cancer lesion reaches the size of 1-2 cm, the cancer will have metastasized to at least one of the sentinel lymph nodes in about one third of patients. Malignant cells break off and drain through the lymph fluid ducts to the lymph nodes and will be apparent in excised lymph nodes if the malignant cells embed in the lymph node. In patients with more advanced disease, the likelihood of spread to sentinel nodes is higher as is the likelihood of spread of the disease to the lymph nodes surrounding the sentinel lymph nodes.
As discussed above, when a tumor lesion is under 1-2 cm, only about ⅓ of patients will have cancer cells in the corresponding lymph nodes, and in the patients where the disease has spread to the lymph nodes, it is often confined to the sentinel lymph nodes.
In the past, a breast cancer patient would normally have a complete axillary lymph node dissection as an adjunct to removal of the primary lesion in the breast. Thus, the patient""s entire lymph node system in the armpit area is removed and biopsied to determine the stage of the cancer and what further treatment was required. However, as discussed above, when the lesion is under 1-2 cm, two thirds of the patients had no migration of cancer cells to the lymph nodes at all, and in others, cancer had only migrated to the sentinel lymph nodes. Thus, total axillary lymph node dissection in two-thirds of the cases were unnecessary. It should be noted that total axillary lymph node dissection can be an extremely painful and debilitating procedure for patients who often suffer from severe lymph edema as a result of the body""s inability to channel the flow of lymph fluid once most or all of the lymph nodes have been excised.
Thus there is a need for methods and devices that can be used to determine the location of sentinel lymph nodes corresponding to a patient""s primary lesion site, and a reliable and noninvasive means of accessing the sentinel lymph nodes to determine whether they are involved in the disease. If the sentinel lymph nodes are determined not to have cancer cells within them, then a total axillary lymph node dissection may be avoided.
It has been known to use radioactive materials or radiopharmaceuticals as localizing agents which can be injected into the area of a primary lesion to monitor the flow of the materials within the patients body using a variety of detectors. Radioactive material such as Technetium 99 m, Indium 111, Iodine 123 or Iodine 125 can be injected in a fluid into the site of a primary lesion and the migration of the radioactive material through lymph ducts to the patient""s corresponding sentinel lymph nodes and other surrounding lymph nodes monitored. Although techniques exist to locate the sentinel lymph nodes of a patient with such radiopharmaceutical tagging, what has been needed are methods and devices to precisely locate and access the sentinel lymph nodes of the patient in a noninvasive manner so as to minimize trauma to the patient should it be determined that a total axillary node dissection is unnecessary.
The invention is directed generally to a method and system for locating and/or accessing specific target sites within the body of a patient. More specifically, the invention is directed to a method and system for locating and accessing a sentinel lymph node of a patient which corresponds to a lesion site within the patient""s body.
In one embodiment of the invention, a radioactive material is injected into a patient""s body near a primary lesion site or other site of interest within the patient. The approximate position of a sentinel lymph node is within the patient""s body is determined by detecting radiation from the radioactive material accumulated within the sentinel lymph node with a radiation detector external to the patient""s body. The sentinel lymph node can then be accessed with a cannula having an RF electrode disposed on a distal end of the cannula by activating the RF electrode to ablate tissue while passing the cannula into the patient""s body until the distal end of the cannula is disposed adjacent the sentinel lymph node. Thus, access to a patient""s sentinel lymph node corresponding to a lesion site is achieved with minimal trauma to the patient, requiring only a hypodermic injection at the lesion site and a channel through the patient""s tissue from the outside surface of the skin to the sentinel node, the channel being no larger than the outside dimension of the cannula.
Once the distal end of the cannula is positioned adjacent the sentinel lymph node, an anchor device can be inserted through the cannula and into the sentinel lymph node. The distal end of the anchor device can then be secured to the sentinel lymph node. Once the distal end of the anchor device is secured to the lymph node, the patient can be transferred to a surgical suite and the lymph node surgically removed with the anchor device attached thereto. The anchor device is thus used as a locator for the sentinel lymph node during the surgical procedure.
In some embodiments of a method of the invention, a gamma camera is used to determine the approximate position of the sentinel lymph node within the patient""s body prior to accessing the sentinel lymph node with the cannula assembly. Alternatively, a hand held radiation detecting wand or the like can be used to determine the approximate position of the sentinel lymph node within the patient""s body. Once the approximate position of a sentinel lymph node is known, the skin of the patient can be marked with a visible mark above the location of the sentinel lymph node prior to accessing the sentinel lymph node with the cannula.
A cannula suitable for use with the method discussed above can have an outer hollow shaft having an inner lumen slidingly disposed about an inner shaft having an RF electrode disposed on the distal end of the inner shaft. The inner shaft can be withdrawn from the outer hollow shaft prior to insertion of the anchor device through the inner lumen of the outer hollow shaft to access a sentinel lymph node. The RF electrode can be an arcuate shaped wire spaced distally from a distal extremity of the distal end of the cannula whereby tissue is ablated along the length of the RF electrode and displaced by the distal end of the cannula as it is advanced through the tissue. Often it is desirable to image the cannula and sentinel lymph node with an ultrasound imaging system during insertion of the cannula into the patient""s body.
The proximity of the distal end of the cannula to a radioactive or xe2x80x9chotxe2x80x9d sentinel lymph node can be determined by inserting a radiation energy detector probe through the inner lumen of the hollow outer shaft of the cannula and detecting an amount of radiation energy emanating from the tissue along the longitudinal axis of the hollow outer shaft. The hollow outer shaft or the radiation energy detector within the outer hollow shaft can be manipulated while in the patient to detect the amount of radiation energy emanating from various portions of the tissue as they pass in front of the distal end of the radiation energy detector during the manipulation.
The relative amount of radiation detected from the various portions of tissue adjacent the longitudinal axis of the hollow outer shaft can be compared by a visual or audio signal or the like in order for the operator of the system to determine the position of the radiation energy detector where the maximum signal strength exists. The input of the radiation energy detector can be configured so as to maximize output signal strength when a hot sentinel lymph node is disposed directly distal of the distal end of the radiation energy detector. Thus, by maximizing the output signal, the operator can determine the precise location of a hot sentinel lymph node.
Once it is confirmed that the distal end of the outer hollow shaft of the cannula is disposed adjacent a hot sentinel node, the distal end of an anchor device can be inserted through the inner lumen of the outer hollow shaft and secured to the sentinel lymph node. The anchor device can be secured to the sentinel node by deploying at least one extension wire from the distal end of the anchor device into the sentinel lymph node. In addition, an outer extremity of the extension wires can be configured to emit RF energy during deployment of the extension wire so as to ablate tissue adjacent a distal end of the extension wire as it is being advanced through tissue during deployment. Ablation energy activation of the distal ends of the extension wires facilitates penetration of tissue during deployment of the extension wires.
An embodiment of an anchor device for locating a desired portion of tissue within a patient can have an elongate shaft with a proximal and distal end. At least one extension wire is disposed at the distal end of the elongate shaft having a withdrawn configuration and a deployed configuration extending from the distal end of the shaft. The anchor device may also include a deployment actuator disposed proximal of the distal end of the elongate shaft and configured to deploy the extension wire from a retracted configuration to an extended configuration. The deployment actuator of the anchor device can be configured to both extend the extension wires and activate RF energy to the extension wires. One embodiment of an anchor device may have markings spaced at predetermined intervals to delineate the diameter of extension of the extension wires.
In one embodiment of an anchor device, an RF electrode is disposed on the distal end of the elongate shaft configured to ablate and penetrate tissue in a manner similar to the RF electrode on the distal end of the cannula discussed above. An RF electrode on the distal end of the elongate shaft can be in the form of an arcuate wire spaced distally from the distal extremity of the distal end of the elongate shaft and optionally may lie in substantially the same plane as the longitudinal axis of the elongate shaft.
A radiation energy detector for locating the position of radioactive tissue within the body of a patient suitable for use with the methods discussed above can be an elongate shaft having a proximal end, a distal end and an outer transverse dimension of the distal end of up to about 4 mm. A detector body is disposed at the distal end of the elongate shaft which is collimated to receive radiation energy at an angle of up to about 30xc2x0, preferably about 10xc2x0 to about 20xc2x0 from a longitudinal axis of the elongate shaft. A detector body signal processor is coupled to the detector body. A handle assembly can be disposed at the proximal end of the elongate shaft of the radiation energy detector. The length of the elongate shaft is typically configured to access to a patient""s tissue through an inner lumen of a cannula and can be about 5 to about 15 cm.
The detector body signal processor can be configured to emit an audible signal to a user of the detector which has an amplitude which increases logarithmically in relation to an increase in the amount of radiation energy being detected. Alternatively, the detector body signal processor can produce a visual signal to a user of the detector which is proportional in amplitude to the amount of radiation energy being detected.
These and other advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying exemplary drawings.